I looked at 80-400VR from Nikon and F-8 together with d800 and compared it to my bellowed lens 70-200/2,8ISMK2 from Canon together with 5dmk2
No problems to se that 80-400 at 200mm together with d800 is a lot sharper
I can see the boards in the wall with the Nikon combo
Not sure why any of the above would need comparing? The D800 is 36mp, the 5D2 is 21mp. At the same focal length, one out-resolves the other. So? Neither of those cameras is a crop sensor, which is what this thread is supposed to be primarily about.
A better comparison would be between the D7100 and the 7D...and with the same Nikon lens...manually focused...with an adaptor for use on the Canon body (since there's no good way to adapt a Canon lens to a Nikon body). That way you could see which sensor resolves more detail at the same focal length. For all I know, it might be a close call, at least at lower ISO.
Then, somehow adapt that new 41mp camera phone to the Nikon lens above, and see if it resolves more detail...and how well it servo autofocuses...while juggling your 5D2 and D800 with the other hand.